1. Field of the Invention
The present invention relates to a digital phase shifter, and more particularly to a digital device and method of generating a signal which is precisely phase-shifted from a reference input signal in an electronic device incorporated in a communication system, a measurement system, and so on.
2. Prior Art
A monostable multivibrator is known as an electronic analog phase-shift means, and a digital counter counting a clock signal is known as an electronic digital phase-shift means. Further, an electromechanical analog phase-shift means is known wherein a plurality of coils through which electric currents having different phases run are combined to generate a rotating magnetic field, in which a magnetic field detection coil that may be set at an optional angle is disposed.
The electronic analog phase-shift method employing a monostable multivibrator is not only susceptible to outside influences, such as change in ambient temperature and power source voltage, but is also unable to cope with an input signal having a high frequency. Even when the frequency of the input signal is not so high, if the amount of phase-shift is large, the analog phase-shift method is unable to cope therewith.
Furthermore, according to the electromechanical analog phase-shift method, it is difficult to accurately set a target phase due to a backlash of a bearing. Further, even though a target phase has been set, the set phase tends to vary because of a mechanical shock to a device including the rotating magnetic field generating coils and the magnetic field detecting coil.
Since the digital phase-shift method can overcome the problems of the analog phase-shift method, the digital phase-shift method needs to employ, when a sufficiently high phase shift accuracy is required, a clock signal having an extremely high frequency and a high speed counter, and thus, sometimes cannot be realized due to the necessity of the high frequency clock signal and high speed counter.